Electricity costs for an air heat exchanger?

Hello Achim, do you mean an air-water heat pump by air heat exchanger? Otherwise, you can read the model on the device, then the type of heating can be determined. Is construction electricity still included in the consumption, e.g., for screed drying? How big is the house? Three people? Do you bathe a lot, constantly keep windows tilted open in winter...? Old freezer chest? Otherwise, the first suspicion would be that the heat pump is running with an electric heater.

If he writes underfloor heating, it can't be an air-to-air system.

It wouldn't be the first air heating new build to be equipped with a purely electric underfloor heating (heating mats) to achieve a somewhat pleasant climate, usually for example in the bathroom. But then the meter spins if you heat the whole house only with that...

Of course, one can speculate wildly, or one can simply accept what is written.

Before the OP clarifies here, your interpretation of the "Luftwärmetauschers" is also just speculation

you are interpreting something into this, not me

Thank you very much in advance for the prompt answers. It is an air-to-water heat pump from alpha-Innotec. The house has about 150 sqm of living space. We do not have a freezer chest, only a state-of-the-art A** refrigerator with a freezer compartment. We generally do not bathe, only shower once a day. But the idea of the heating rod might not be bad either. I need to look into that idea. How can I recognize that?